Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA fragments containing whole genes, but it can also be used to amplify any DNA sequence such as promoters, non-coding sequences and randomly fragmented DNA
It is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting to large scale protein production.
Occasionally, the term cloning is misleadingly used to refer to the identification of the chromosomal location of a gene associated with a particular phenotype of interest, such as in positional cloning
In practice, localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence
Dolly the Sheep
Dolly, a Finn-Dorset ewe, was the first mammal to have been successfully cloned from an adult cell.
Dolly was formed by taking a cell from the udder of her biological mother. Her embryo was created by taking the cell and inserting it into a sheep ovum.
The embryo was then placed inside a female sheep that went through a normal pregnancy.
She was cloned at the Roslin Institute in Scotland and lived there from her birth in 1996 until her death in 2003 when she was six.
Cloning Dolly the sheep had a low success rate per fertilized egg; she was born after 277 eggs were used to create 29 embryos, which only produced three lambs at birth, only one of which lived.
Seventy calves have been created and one third of them died young; Prometea took 814 attempts.
Notably, although the first clones were frogs, no adult cloned frog has yet been produced from a somatic adult nucleus donor cell.
Early claims that Dolly the Sheep had pathologies resembling accelerated aging.
Scientists speculated that Dolly's death in 2003 was related to the shortening of telomeres, DNA-protein complexes that protect the end of linear chromosomes.
Other researchers, including Ian Wilmut who led the team that successfully cloned Dolly, argue that Dolly's early death due to respiratory infection was unrelated to deficiencies with the cloning process.
Human cloning is the creation of a genetically identical copy of an existing or previously existing human.
The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction.
There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning.
Therapeutic cloning involves cloning adult cells for use in medicine and is an active area of research.
Reproductive cloning would involve making cloned humans.
A third type of cloning called replacement cloning is a theoretical possibility, and would be a combination of therapeutic and reproductive cloning.
Replacement cloning would entail the replacement of an extensively damaged, failed, or failing body through cloning followed by whole or partial brain transplant.
The various forms of human cloning are controversial.
There have been numerous demands for all progress in the human cloning field to be halted.
Most scientific, governmental and religious organizations oppose reproductive cloning.
The American Association for the Advancement of Science (AAAS) and other scientific organizations have made public statements suggesting that human reproductive cloning be banned until safety issues are resolved.
Serious ethical concerns have been raised by the future possibility of harvesting organs from clones.
Some people have